Backscatter is promising to deliver near-zero-power communications for billions of ZigBee devices. However, existing backscatter tags face two practical challenges. Firstly, the deployment depends on dedicated excitors or additional receivers, driving up costs. Secondly, the modulator couples phase modulation with multiple high-frequency shifting clocks, boosting tag power. We propose BumbleBee, a pervasive, universal, and efficient ZigBee backscatter design. It reuses uncontrolled Bluetooth and proprietary FSK devices as excitors and demodulates with a single commodity receiver, slashing deployment cost. The key innovation of BumbleBee lies in overwrite modulation, which embeds tag data through dominant phase shifts, effectively overwriting ambient excitation content. The implementation of overwrite modulation depends on a novel Multi-Phase Shift (MPS) modulator that decouples baseband modulation from frequency shifting control, cutting clock requirements. These techniques benefit not only ZigBee but also other protocols that decode via the sign of phase shifts, as shown by a BLE5 backscatter extension. Our prototype uses commodity BLE4/FSK-based SDR excitors, an off-the-shelf FPGA, and commodity ZigBee/BLE5 receivers. Experiments show that BumbleBee achieves 223.2 kbps for ZigBee backscatter and 890.7 kbps for BLE5, 10x better than FreeRider [1], while MPS reduces power by 3.5x.

We present EchScatter, a novel backscatter system that takes productive ZigBee signals as excitations and enables high-throughput ZigBee backscatter communication. Compared with the existing ZigBee backscatter, EchScatter does not need to control the carrier, ensuring the universality of the transmitter. EchScatter has realized chip-level modulation of productive ambient ZigBee backscatter for the first time. It is capable of transmitting more tag bits simultaneously, thus increasing the throughput of the system. We first design 16 different 32-chip phase modulation sequences to realize the translation of any two ZigBee symbols. Therefore, our system can transmit four tag bits through one symbol. After that, we use an average energy detection-based synchronization method to make sure the synchronization error of the EchScatter meets the requirements of chip-level modulation. We prototyped EchScatter using an off-the-shelf FPGA and commodity ZigBee transceivers. Through extensive experiments and field studies, we show that EchScatter can work universally on commodity ZigBee transceivers. In line-of-sight and non-line-of-sight scenarios, EchScatter is able to achieve 247 kbps and 245 kbps throughput at a signal strength of around -60 dBm, respectively. The throughput of EchScatter is 32 times higher than that of FreeRider. We believe it will have more pervasive applications.

Existing IoT systems suffer from restricted communication distances, high deployment costs, and frequent battery replacements, making them ineffective for managing healthcare data. This paper presents Prometheus, a self-powered wristband for reporting personal health status over long distances and intelligently managing healthcare data. Prometheus backscatters ambient BLE and ZigBee signals for low-power communication while incorporating a multi-source energy harvester to convert ambient RF, light, and heat into electricity. It also features a biochemical sensor array for monitoring sweat biochemical markers. Prototyped on a flexible PCB, Prometheus demonstrates impressive efficiency, consuming only 5.8 mW for sweat sensing, with BLE and ZigBee transmission energies significantly lower than standard electrochemical workstations and commercial alternatives. Our experiments show consistent signal quality at distances up to 20 meters. In summary, Prometheus emerges as a convenient, efficient, and self-powered wristband, promising to provide ubiquitous healthcare data management in our lives.

Codeword translation is well-known for translating excitation signals into other codewords to provide productive ZigBee backscatter. But the limited throughput of conventional systems using info-rich codewords to transmit a single bit challenge their effectiveness to perform sensor-data transmission. In this paper, we introduce ChipScatter, a novel high-throughput modulation technology that translates excitation codewords into more controllable codewords through fine-grained chip-level modulation. The more controllable categories available, the more bits can be transmitted simultaneously. Evaluation results show that ChipScatter can increase the throughput of productive ZigBee backscatter by up to 8×.

We present BumbleBee, a novel backscatter system that creates ZigBee transmissions over productive Bluetooth Low Energy (BLE) carriers. In contrast to prior content-aware or non-productive backscatter, BumbleBee overwrites tag information independently on any ambient BLE. The backscattered signal is dominated by the tag information and compliant with commodity ZigBee radios. Since BLE signals are widespread, BumbleBee enables the vision of pervasive ZigBee backscatter communication. We prototype BumbleBee using commodity BLE transmitters, an off-the-shelf FPGA, and commodity ZigBee receivers. Through extensive experiments and field studies, we show that BumbleBee works universally with ambient BLE and commodity receivers. Further, when the signal strength is -80 dBm, BumbleBee has a throughput of 218 kbps and 204 kbps in the line-of-sight (LOS) and nonline-of-sight (NLOS) scenarios, respectively. The throughput improvement is up to 3x compared with the advanced non-productive backscatter system, Interscatter [1], and$32\mathrm{x}$over the content-aware backscatter system, FreeRider [2]. The bit error ratio (BER) is below 1% when the tag-to-receiver distance is 20 meters. As the first ambient ZigBee backscatter system that works universally with commodity transceivers, we believe BumbleBee takes a crucial step towards pervasive ZigBee backscatter communication.

To piggyback information, the instantaneous-phase shift (IPS) modulation toggles discrete phases on ambient RF carriers, which is popular with advanced backscatter systems. However, IPS has poor spectrum efficiency. It produces serious spectrum sidelobes and prevents the formation of large networks. In this paper, we propose frequency-phase shift (FPS) modulation, a fine-grained RF switches toggling that modulates carriers with a continuous phase shift. The phase continuity suppresses spectrum sidelobes without disturbing the demodulation results. We first apply FPS to optimize a ZigBee backscatter tag. ZigBee signals, consisting of a non-single-tone header and a single-tone payload, are transmitted as RF carriers. The backscatter tag leverages FPS to modulate the single-tone for phase-continuity data transmission. Further, the tag recycles the non-single-tone header using sub-symbol codeword translation to improve carrier utilization. Through extensive experiments and field studies, we demonstrate that FPS enables ZigBee transmissions with a bandwidth of 2.4 MHz, which is 3x lower than that of Interscatter [1] and much closer to active radios. The system prototype consists of a microchip transmitter, a backscatter tag, and a commodity receiver. Specifically, when the transmitter-to-tag distance is within 5 centimeters, the system enables a goodput of 16.6 kbps at a channel capacity of 16.8 kbps, and the communication distance can be extended to 17 meters.